Dr. S. Sujatha
Scientific Officer

Ph: +91 80 4091 4507
Fax: +91 80 2238 5957
E-mail:
sujatha@mpbifr-blr.in

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Research Areas:

• Photometry of open clusters
• Spectroscopy of Ap stars

• PhD., Physics (Astrophysics), Bangalore University, 2008
• MSc, Physics, Bangalore University, 2000
• BSc, Mount Carmel College, Bangalore, 1998

• Scientific Officer, MPBIFR, 2008 – till now
• Research Scholar, MPBIFR, 2004 – 2008
• Lecturer at Mount Carmel College, 2000 – 2004

Research Areas:

Photometry of open clusters

It is well known that stars are born as clusters initially and over time these clusters evaporate and/or disrupt enriching the general field population. Open clusters are formed in the Galactic disc and are distributed throughout it. They are ideal objects for focusing on several astrophysical problems, such as star formation, stellar evolution and dynamic evolution of stellar systems as well as chemical evolution of the Galactic disc. Emergence from their gaseous and dusty cocoons highlights the interaction of stellar systems with the interstellar medium (ISM). Analysis of the Galactic cluster population, either as a whole or in age groups has provided wealth of insight on the morphology and dynamics of spiral arms, the various scales of Milky Way (disk heights, distance to Galactic centre, extension of the warp, flare, and others), Galactic rotation, formation and development of the Milky Way.

According to the recently updated version 3.0 (20 April 2010) of the Dias et al.’s (2002, http://www.astro.iag.usp.br/~wilton) open cluster catalogue, 2095 open clusters exist in the Milky Way disc. Unfortunately, fundamental parameters like distances, reddening and ages are available for fewer than half of the open clusters in this sample. The study of open clusters, especially the estimation of their distances, is very valuable for a better understanding of galactic spiral structure. All we know about the majority of the catalogued clusters are their positions and approximate angular sizes, which are inaccurate in many cases. To examine or for better understanding of mass function (MF) of clusters, we must improve the statistics of well-studied open clusters. In fact, the greater the number of clusters with well determined cluster parameters like cluster membership, distances, reddening and ages would lead to more accurate estimation of MF.

Spectroscopy of Ap stars

The study of stars begins with the knowledge of its spectral type. In the early 1900s, E. C. Pickering, Annie Cannon and their colleagues at the Harward Observatory set up th spectral classification scheme, which we use today. According to this scheme, the stars are classified into O B A F G K M types depending mainly upon their surface temperatures and also their chemical compositions. The different types of stars have been studied for quite a long time. Among them the study of A type stars has been somewhat unique as some stars of this type have been found to show anomalous overabundances of certain elements like the Si, Sr, Cr and rare earths as compared to the normal stars of the same kind. The A type stars with the above mentioned anomalies are termed as “peculiar A type stars” and denoted as Ap stars. The other observed anomalies of the Ap stars are under abundance of the helium in most of the star, small deficit in the light elements C, O, Mg, Si in some stars, Ca deficit in most stars, 10 to 100 fold excess of the elements like Sc, Ti, Cr, Mn, Fe in many stars, excess of elements like Sr, Y, Zr up to 1000 times, excess of rare-earths like La, Eu, Gd, Dy by factors of 300 to 1000 and more.

Many of the Ap stars have been found to show photometric and spectroscopic variations in addition to the variation in magnetic field strengths. The need for the knowledge of physical parameters of Ap stars has been strongly felt and hence studies have been carried out at MPBIFR in different lines like photometric, spectroscopic and study of magnetic field strengths.

1. M.Phil research project titled “Study of the physical parameters of young open clusters” by Sowmya S. Kulkarni.
   Dissertation submitted in partial fulfilment of the requirements for the degree of Master of Philosophy in Physics prescribed by the Christ University, Bangalore. M.Phil degree awarded in 2010.

2. M.Sc., Project titled “Study of faint young galactic open clusters” by S. Lalitha and Paul Vinjeet
   Project submitted as a partial fulfilment for the requirement of the Masters Degree in Science (Physics) prescribed by the Christ University, Bangalore. Degree awarded in 2008.

3. B.E. Project titled “Haffner package for Open Clusters” by J. S. Amoghavarsha and Debolina Das
   Project report submitted as a partial fulfilment for the requirement of the Bachelors Degree in Computer Science and Engineering prescribed by the Visveswaraiah Technological University, Bangalore. Degree awarded in 2005.

Membership of professional organizations:

1. Member of International Astronomical Union - Division IX Commission 25 Stellar Photometry and Polarimetry.
2. Life member of Astronomical Society of India.
3. Life member of Indian Physics Association.

Publications list (Selected):

1. “Mass function of open clusters NGC 1857 and Czernik 25”
   Sujatha, S., Babu, G.S.D. and Sharath Ananthamurthy, Bulletin of Astronomical Society of India, 34, 357 – 373, 2006.
2. “NGC 1624 (OCl 403, Cr 53)– A very young open cluster”
   Sujatha, S. and Babu G.S.D., Astrophysics and Space Sciences, 305, 399 - 410, 2006.
3. “UBVRI CCD photometric studies of open clusters Berkeley 15, Czernik 18 and NGC 2401”
   Sujatha, S., Babu G.S.D. and Sharath Ananthamurthy, Bulletin of Astronomical Society of India, 32, 205- 309, 2004.
4. “Variation of the Si II features in the chemically peculiar star – HD 115735”
   Sriraghavan, S. M., Jayakumar, K., Babu, G. S. D., and Sujatha, S., Bulletin of Astronomical Society of India, 32, 113-119, 2004.
5. “Study of Old Open Clusters NGC 1605, Czernik 18 and NGC 2509”
   Sujatha, S. and Babu G.S.D., Bulletin of Astronomical Society of India, 31, 379-382, 2003.
6. “Spectral Line Variations in the Ap Star HD42536”
   Babu, G. S. D., Jayakumar, K. J., Velu, C., and Sujatha, S., Bulletin of Astronomical Society of India, 31, 337-339, 2003.
7. “Study of Open Cluster NGC 2509”
   Sujatha, S. and Babu, G.S.D., Bulletin of Astronomical Society of India, 31, 9-18, 2003.

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